I agree that xylitol is great for dental health, especially for kids. But it is deadly to dogs. It only takes one piece of gum or candy to kill a 20-pound dog. I used to give my kids gum from my secret stash, but the oldest found it, started taking several pieces at a time, and dropped one on the floor. One of our schnauzers found it. Thankfully, the kid fessed up right away, and I was able to induce vomiting in the dog(1-3 tablespoons of hydrogen peroxide). The dog is a little piggy and swallows everything whole, so it came back up in one solid piece with the coating still intact.
I only learned about this toxicity a couple of years ago, and felt obligated to dog owners to share.